Resistive gas sensors based on colloidal quantum dot (CQD) solids for hydrogen sulfide detection

Colloidal quantum dot (CQD) is emerging as new substitution gas sensing materials due to the excellent accessibility of gas molecules to CQD surfaces realized via surface ligand removal. Here we demonstrated highly sensitive and selective H2S gas sensors based on PbS CQD solids. The sensor resistance decreases upon H2S gas exposure and the response is defined as the ratio of the sensor resistance in clean air to that in H2S gas. As the operating temperature increased within the range 50–135°C, the sensor response increased while the response and the recovery time decreased. The sensor was fully recoverable toward 50ppm of H2S at 108°C and the highest response was 2389 at 135°C with the response and recovery time being 54s and 237s, respectively. The dependence of sensor response on the H2S gas concentration in the range of 10–50ppm is linear, suggesting a theoretical detection limit of 17ppb toward H2S at 135°C. Meanwhile, the sensor showed superb response selectivity toward H2S against SO2, NO2 and NH3. We propose that the PbS CQDs film where the surface states determine the conduction type via remote doping may undergo a p-to-n transition due to H2S exposure at elevated temperatures.